Filament winding is an established technique for producing essentially hollow, light-weight articles or components with a stiff, rigid skin. Components made by this technique are generally those which have a constant cross-section, such as pipes. Filaments, strands or tows impregnated or coated with thermosetting resin are wound tightly around a mandrel or former, and allowed to cure or set to form a hard skin. The technique has the ability to produce components of low weight and high rigidity. In order to achieve the desired low mass and low inertia in the finished article, the mandrel is removed after the resin has set, to leave the article in its final, hollow condition.
A problem with the production of complex shapes by filament winding techniques is that of removing the mandrel. It is possible to make the mandrel from a low melting point allow, and then to melt the alloy so that it flows out. Disadvantages of this method are the consequent weight of the mandrel which then has considerable inertia resulting in difficulties in accelerating and decelerating the mandrel during the winding process, and the heat energy and labour involved in melting the alloy and in reforming it for subsequent cycle. Such alloys also deteriorate over a number of cycles.
A variety of other mandrel constructions and removal methods are also known.